Integrated circuit manufacturing tolerances on critical field effect (FET) device parameters can affect device performance. For example, variations in gate dielectric (often an oxide) thickness, FET channel length and threshold voltage will produce skews in performance and in power consumption creating distributions referred to as fast, nominal and slow process, or alternatively as best-case, nominal and worst-case product corners.
Further, as dielectric thicknesses have decreased, tunneling leakage has become an appreciable fraction of the total integrated circuit power consumption. Tunneling leakage is especially problematic for the best-case or fast process distribution, because the faster devices draw more current than slow devices. In the absence of speed sorting, the speed of integrated circuits is specified at the slowest end of the distribution to insure all manufacturing output can be sold. An integrated circuit with fast processing will therefore be sold for performances slower than its actual capabilities and will conduct the highest amount of gate leakage.
Device dielectric tunneling leakage current can also affect burn-in of integrated circuits. During burn-in, a static voltage that is a multiple of the normal operating voltage of the integrated circuit is applied to the integrated circuit in order to force devices with weak gate dielectrics and other defects to fail. A typical burn-in condition multiplies the normal power supply between 1.1× and 1.5×, which results in a static tunneling current increase. Burn-in power dissipation can be 60 watts compared to about 20 watts at the normal, lower power supply. At these higher burn-in voltages power dissipation of the integrated circuit can be high enough to cause catastrophic failure of both the integrated circuit and the associated burn-in boards and other equipment.
Therefore, a method of compensating for tunneling leakage that will reduce the power consumption of fast integrated circuit chips and the power distribution of integrated circuits chips during burn-in is needed.